Over the course of the last twenty (20) years it has been debated whether the release of chlorofluorocarbons (CFCs) into the atmosphere has effected the stratospheric ozone layer. As a result of this debate and international treaties, the refrigeration and air-conditioning industries have been weaning themselves from the use of CFCs and hydrochlorofluorocarbons (HCFCs). Presently, the industries are transitioning towards the use of hydrofluorocarbons (HFCs) having zero ozone depletion potential, as well as other fluorocarbon refrigerants not containing chlorine. Notably, this transition to HFCs necessitated the advent of a new class of lubricants because of the immiscibility of non-oxygenated conventional lubricants, such as mineral oil, alkylbenzene, and poly-α-olefin, with HFC refrigerants.
As a result of the transition from CFC and HCFC to HFC and other fluorocarbon refrigerants in vapor compression refrigeration systems, many CFC and/or HCFC based systems currently installed in the field will require retrofit. However, the non-oxygenated conventional compressor lubricants used with CFCs and HCFCs are not miscible with HFC refrigerants under refrigeration system operating conditions. While attempts have been made to use non-oxygenated and relatively non-polar conventional lubricants with relatively polar hydrofluorocarbon refrigerants in refrigertion systems, the lack of solubility of the HFC refrigerant in the non-oxygenated conventional lubricant renders this combination unsuitable for use in refrigeration sytems due to the presence of the highly viscous, immiscible, non-oxygenated lubricant in non-compressor zones of a refrigeration system. This incomparable combination also causes an undesirable coating of the non-compressor zones of a refrigeration system with the non-oxygenated lubricant if non-oxygenated lubricant is not thoroughly flushed from the system during retrofit. The presence of residual non-oxygenated lubricant in a vapor compression system can form a second phase, particularly in the evaporator and condenser, which can interfere with heat transfer and result in reduced system energy efficiency and capacity. Therefore, most compression refrigeration systems require costly and time-consuming flushing to remove non-oxygenated conventional lubricants and replace them with lubricants which are miscible with HFCs, such as polyol ester (POE), polyalkylene glycol (PAG) and polyvinyl ether (PVE) lubricants.
Accordingly, there exists a need and an opportunity to resolve this solubility problem so that the refrigeration industry may retrofit systems without costly and time-consuming flushing to entirely remove conventional lubricants. The present invention satisfies this need of the industry.